In a typical vehicle, such as a four-wheel drive pick-up truck or the like which provided with a snow plow and is adapted to remove snow from roads, parking lots, driveways, and other surfaces, by pushing the snow, the plow is mounted to the front of the truck. The plow is mounted in conjunction with a means for raising and lowering the plow, such as by hydraulic pumps and the like so that the plow can be placed on the surface to be plowed and can be lifted from the surface when the plow is not in use.
Modern snow plows of this type contain a switch located in the cab of the truck to actuate the hydraulic pump and move the plow between a raised position and a lowered position. Oftentimes, there is a single switch which may be mounted on the dash, particularly in the case where the vehicle has an automatic transmission, or on the manual transmission shift lever when that form of transmission is in the truck, so that the operator can move the switch from a raising position to a lowering position as desired. In some cases, there is a middle or hold position for the switch. Depending upon the sophistication of the design, limit switches and springs may be used in conjunction with the control switch to limit or control the movement of the plow in an up or down direction. Additionally, switching means may be provided to shift the angle of attack of the plow to the left or right as desired.
Oftentimes, a truck with a snow plow will be used to clear large areas which have been covered with snow, such as shopping center and school parking lots, which are best cleared by pushing snow to one side of the lot or possibly to several sides in said large lots. These lots often have pylons or cement barriers to align parking spaces, but these objects make single pass snowplowing impossible. The best procedure for removing snow under these conditions involves repeated changing of direction as snow is pushed forward in drive or one of the forward gears, and the truck is backed up in reverse to approach a different area of snow covered pavement. As the lot becomes clear of snow, the need to change direction increases, particularly where the lot contains pylons and other barriers. This back and forth movement is best accomplished when the plow is raised during the reverse travel of the vehicle to avoid damaging the plow, followed by lowering the plow to again engage the snow in the next area being cleared. While this is not difficult over a short period of time, efficient operation of such a snow plowequipped truck requires the coordinated effort of two hands to do three tasks, namely, steer, shift, and adjust the plow height. If the plow is not raised when backing up oftentimes snow is redistributed over areas which have already been cleared. Additionally, the angle of the plow may be adjusted during this time calling for a fourth task at one time.
Owners of this kind of equipment are often independent operators, not having the massive snow plows that municipal and state government agencies employ. Operators of these plow-equipped trucks may work for as long as fifteen to eighteen hours at one time, or even longer. Independent operators need to make money when the opportunity exists, such as when a snowfall is fresh, and so speed of operation is important. Also important is the need to service as many customers as possible as soon as the snowfall has begun to subside. Naturally, fatigue, both physical and mental, begins to set in during this relatively difficult yet monotonous job. The ability to coordinate the steering wheel, the transmission shift lever and the plow switch becomes more difficult. The operation becomes slower or mistakes are made.
At the present time, there is no commercially available device which can be used to improve on the efficiency and reduce the fatigue of operating a truck fitted with a snow plow. While many manufacturers provide snow plows which are highly suitable for mounting on four-wheel drive vehicles, none of these manufacturers provide any equipment which can obviate the need to coordinate three tasks with two hands.
U.S. Pat. No. 2,824,849 describes a mechanical method for raising and lowering snow plows on motor vehicles. Such a design is extremely heavy duty and has been improved upon substantially by more modern designs. Larger equipment, such as that shown in U.S. Pat. No. 4,258,484 relates to grader-type snow plows used for clearing along highways. This design is most often not even capable of being used for parking lots and other areas which require maneuverability and the capability of back-and-forth operation.
In some construction equipment, such as rippers, as described in U.S. Pat. No. 4,031,964 sensitivity to an overload condition is described wherein lift cylinders are actuated to automatically raise a shank when an overload is applied to the shank during ripping operation. In that patent, a complicated design of electromagnetic valves and means for detecting overloads are employed.
Smaller plow products such as snow plows which are fitted to four-wheel drive vehicles are, as has been mentioned, readily available. Nevertheless, none of these designs resolve the problems noted above concerning the need for three functions being performed at one time, and no equipment is available to reduce fatigue or operator error due to fatigue.